Code Applied by the app hvac.ventilation.outdoor-air
Outdoor air for ventilation
Occupied spaces get a code minimum of outdoor air, set by the kind of room, the people in it and its floor area (a dining room 7.5 CFM a person plus 0.18 a square foot); on a bid the question is whether the plan's supply already carries it or a separate unit does.
| When | The app uses |
|---|---|
| outdoor air to an occupied space, by mechanical or natural ventilation | required |
| the minimum, by occupancy | per person plus per floor area |
| a dining room, per person | 7.5 cfm/person |
| a dining room, per square foot of floor | 0.18 cfm/ft² |
- Source
- IMC · 403 Mechanical ventilation (rates in Table 403.3.1.1) · read the public text
- Editions checked
- 2021
- Used by
- Courses
- Amendments
No state or local amendment to this rule is on file. Not on file means the model code as written — check your jurisdiction.
A model code the authority having jurisdiction adopts.
Every occupied room needs fresh outside air, and the code sets the minimum by what the room is used for: an amount per person and an amount per square foot of floor. A dining room, for one, is 7.5 CFM a person plus 0.18 a square foot, at a default of 70 people per 1,000 square feet. The engineer does that arithmetic. It sets how much of a room's supply must be outside air, not the supply itself: the cooling load sets the supply, and only in a crowded room with a small load does the ventilation push the supply up.
The estimator's job is to read where it landed: an equipment schedule that gives each rooftop unit its outdoor-air CFM, and a room air schedule that says its supply includes the ventilation, mean the rooftop units bring the outside air in through their economizers or outside-air dampers, and nothing more is priced. A set that shows a dedicated outdoor-air unit, or outside-air ducts to each unit, is more equipment and more duct.
What the app does with it
Nothing automatic. Bid Check's OA meets code row is a manual tick you make once you have read the schedule's outdoor-air number and its note, or found the outdoor-air equipment. The Room Sizer's airflow by room type is supply air for sizing, not this minimum (see the room airflow rule).
Verify against your edition
The table's rates are ASHRAE 62.1's Ventilation Rate Procedure: the dining room's 7.5 and 0.18 read the same in the Seattle 2021 Mechanical Code (the IMC with Washington amendments) and in an older IMC Table 403.3. Some adoptions allow a design to ASHRAE 62.1 directly instead of the table, and an engineered design may reduce the rate; the rates also move between editions. Local amendments still govern: the numbers belong to the engineer and the adopted code.
Settled 2026-09-27 by Claude on the owner's delegation, from the dossier's research and the model code text; not checked against a printed book or a local amendment.
Cited by section, not reprinted: the code text belongs to its publisher. Company practice is not a rule here — it lives with your pricing.